The present invention relates to an immortalized bone marrow mesenchymal stem cell obtained by transferring a cell proliferation factor gene into a bone marrow mesenchymal stem cell.
It has been reported by various researchers that bone marrow mesenchymal stem cells differentiate into bone cells, chondrocytes, adipocytes, myocytes, tendon cells, cardiomyocytes. Therefore, it has been expected that if the bone marrow mesenchymal stem cells can be propagated in large numbers in vitro with the pluripotency kept, the resulting bone marrow mesenchymal stem cells will be a very valuable means for regenerative medicine.
As an example other than a bone marrow mesenchymal stem cell, it is known that a cell-line which maintains appropriate functions for differentiation can be produced by transferring an oncogene to BSMC, MDHF or RKC to immortalize each of the cells (K. A. Westerman, et al., Proc. Natl. Acad. Sci., USA., vol 93, 8971, (1996)). If the method is used, it is possible to obtain those immortalized cells in large numbers. However, when each of the immortalized cell-lines is infused into a living body, there is the problem of a possibility that the patient is exposed to unexpected risk of malignant transformation. Therefore, it is difficult to obtain highly safe bone marrow mesenchymal stem cells which can solve such a problem, in large numbers.
The object of the present invention is to provide immortalized bone marrow mesenchymal stem cells which can proliferate indefinitely and have a means to avoid a possibility of malignant transformation.
As a result of making an intensive study in view of the above situation, the present inventors have found the followings and completed the present invention. The present inventors have found that bone marrow mesenchymal stem cells, which have a means to avoid risk of malignant transformation and can proliferate in large numbers, can be obtained by transferring to bone marrow mesenchymal stem cells a cell proliferation factor gene which is derived from a normal cell and inserted between a pair of site-specific recombination sequences.
Therefore, the present invention provides an immortalized bone marrow mesenchymal stem cell obtained by transferring a cell proliferation factor gene inserted between a pair of site-specific recombination sequences to a bone marrow mesenchymal stem cell.
In the immortalized bone marrow mesenchymal stem cell, the bone marrow mesenchymal stem cell is preferably a human bone marrow mesenchymal stem cell.
In the immortalized bone marrow mesenchymal stem cell, the cell proliferation factor gene is preferably hTERT (human telomerase reverse transcriptase) gene.
In the immortalized bone marrow mesenchymal stem cell, the pair of site-specific recombination sequences is preferably LoxP sequence.
Further, it is preferable that the cell proliferation factor gene is transferred using a retroviral vector.
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